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森林结构驱动热带次生林演替过程中光异质性的变化
Journal of Ecology
(
IF
5.3
)
Pub Date : 2021-04-30
, DOI:
10.1111/1365-2745.13680
Tomonari Matsuo
1
,
Miguel Martínez-Ramos
2
,
Frans Bongers
1
,
Masha T van der Sande
1
,
Lourens Poorter
1
Affiliation
- Forest Ecology and Forest Management Group Wageningen University Wageningen The Netherlands.
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad Universidad Nacional Autónoma de México Morelia Michoacán México.
光是树木性能的关键资源，因此，树种划分光可用性的空间和时间梯度。尽管光分布在次生林演替过程中驱动着树木的表现和物种更替，但我们仍然缺乏了解光分布如何随着热带森林的发展而变化。
本研究旨在评估森林结构的变化如何导致热带森林演替过程中垂直和水平光异质性的变化。
我们使用时间顺序方法描述了光的演替模式，其中我们比较了自农业废弃以来年龄不同（8-32 年）的 14 个墨西哥次生林。对于每个林分，我们测量了 16 个网格单元中的垂直光剖面，以及每棵树的结构参数（胸高直径、高度和树冠尺寸）。
在演替过程中，我们发现林分大小（底面积、冠面积和长度）和林分分化（即沿森林轮廓逐渐分布的叶子）迅速增加，这导致光照条件的快速变化和更多的光照异质性。垂直光梯度的拐点（即达到50％相对光强度的绝对高度）在前20年迅速向更高的高度移动，表明有冠层树木拦截了更多的光。由于树冠面积随高度的积累变慢，光衰减率（即消光率）在演替过程中降低。由于树冠尺寸的增加和侧向间隙频率的降低，林下光强度和异质性在演替过程中略有下降。废弃后32年，林下相对光强度为1.56%。
合成。在演替过程中，光照条件线性变化，这应该导致物种的连续不断的更替。特别是在演替后期，较强的垂直光照梯度可以限制需光先锋物种的再生，并增加冠层下耐荫后期演替物种的比例。光照条件的这些变化很大程度上是由森林结构的连续变化驱动的，因为断面积强烈决定了吸收大部分光的高度，而树冠面积和较小程度上的树冠长度决定了光分布。
"点击查看英文标题和摘要"
Forest structure drives changes in light heterogeneity during tropical secondary forest succession
- Light is a key resource for tree performance and hence, tree species partition spatial and temporal gradients in light availability. Although light distribution drives tree performance and species replacement during secondary forest succession, we yet lack understanding how light distribution changes with tropical forest development.
- This study aims to evaluate how changes in forest structure lead to changes in vertical and horizontal light heterogeneity during tropical forest succession.
- We described successional patterns in light using a chronosequence approach in which we compared 14 Mexican secondary forest stands that differ in age (8–32 years) since agricultural abandonment. For each stand, we measured vertical light profiles in 16 grid cells, and structural parameters (diameter at breast height, height and crown dimensions) for each tree.
- During succession, we found a rapid increase in stand size (basal area, crown area and length) and stand differentiation (i.e. a gradual leaf distribution along the forest profile), which leads to fast changes in light conditions and more light heterogeneity. The inflection points of the vertical light gradient (i.e. the absolute height at which 50% relative light intensity is attained) rapidly moved towards higher heights in the first 20 years, indicating that larger amounts of light are intercepted by canopy trees. Light attenuation rate (i.e. the rate of light extinction) decreased during succession due to slower accumulation of the crown area with height. Understorey light intensity and heterogeneity slightly decreased during succession because of an increase in crown size and a decrease in lateral gap frequency. Understorey relative light intensity was 1.56% at 32 years after abandonment.
- Synthesis. During succession, light conditions changed linearly, which should lead to a continuous and constant replacement of species. Especially in later successional stages, stronger vertical light gradients can limit the regeneration of light-demanding pioneer species and increase the proportion of shade-tolerant late-successional species under the canopy. These changes in light conditions were largely driven by the successional changes in forest structure, as basal area strongly determined the height where most light is absorbed, whereas crown area, and to a lesser extent crown length, determined light distribution.
更新日期：2021-04-30
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